Muffler liner



Nov. 5, 1963 Filed June 7, 1960 G. SLAYTER ETAL 3,109,511

MUFFLER LINER 2 Sheets-Sheet 1 12ml LL H INVENTORS GAMES SLAYTER,

BY Ross/er G Passe-LL & Mama l. MORGAN AT romvsys Nov. 5, 1963 SLAYTER ETAL MUFFLER LINER 2 Sheets-Sheet 2 Filed June 7, 1960 INVENTORS Q 6 6 man Y 50 UM N R L6. m 5 7 3 J MW 6P United States Patent 3,109,511 MUFFLER LENER Games Slayter, Newark, Robert G. Russell, Granville,

and Willard L. Morgan, Newark, Ohio, assignors to Owens-Corning Fiberglas Corporation, a corporation of Delaware Filed June 7, 1960, Ser. No. 34,408 2 Claims. (Cl. 181-61) This invention relates to an improved muffling system and more particularly to a vehicle mufiling system in which components are lined with highly refractory fibers.

Present mufllers include casings or walls of one or more wraps of steel which enclose a plurality of internal steel baffies to mufile the sound of the engine and exhaust gases. These mufllers are subjected to conditions which cause the casings to be attacked with the result that the mufllers are relatively short lived. For example, particularly in winter and on short trips, liquids of an acidic nature from the engine will deposit on and attack the interior surface of a mufiler casing. On long trips the mufiler casing also tends to become very hot, the gases within the casing often being over 1600 F. under normal operating conditions and may be substantially higher than this if a spark plug is not functioning with the result that a cylinder exhausts a mixture of air and raw fuel into the exhaust system where it burns partially. Oil expelled from the engine through the exhaust system, and deposited in the mufller, may also smolder and thereby further increase interior temperatures. Elevated muffler casing temperatures increase the rate at which the casing oxidizes orrusts.

There is also reason to believe that conventional muffiers may increase the amounts of certain deleterious contaminants in exhaust gases. Available evidence indicates that exhaust gases in contact with hot iron or steel undergo a reaction which increases the amounts of olefins in the gases. This reaction can occur in conventional muffling systems, wherever exhaust gases contact hot steel or oxidized cast iron components of an exhaust system.

In addition, the bare metal walls of conventional mufflers and muflling systems extract heat rapidly from the exhaust gases, thus causing the gases to cool rapidly. Such cooling prevents secondary combustion in the exhaust system that might otherwise consume at least part of the carbon monoxide and olefins in the exhaust gases. In present mufiling systems, secondary combustion is very rare and may only occur at high operating speeds when raw fuel and air flow through the exhaust system.

The present invention relates to a muflling system having a lined component and to an insulating liner which overcomes the above-discussed disadvantages of existing mufliing systems. The liner is preferably made of highly refractory fibers held together by a suitable binder, the liner being located near the inner surface of the component, between it and the exhaust gases. There is a much smaller tendency for condensation to occur with the new exhaust system because the exhaust gases are kept out of contact with the cold walls of the system, and because the liner remains hot longer after the engine is stopped. Any such liquid that does condense, as in winter when the engine is not operated for a long enough period to heat the liner sufficiently, will eventually evaporate in the exhaust gases and thereby be carried out of the exhaust system without doing any damage. The insulating liner also maintains the outer metal walls of the exhaust system components at much lower temperatures by comparison with conventional systems, the walls being approximately 300 F. or less when the exhaust gases are 1600 F. when a liner only one-half inch thick is used. The relatively coo'l walls thus tend to oxidize,

rust, and warp to a much smaller degree than formerly and no special steels are required for the muffler components as might otherwise be necessary. In addition, the new liner prevents contact between the exhaust gases and the steel or cast iron walls of the lined exhaust system component and thus prevents an increase in the amount of olefins which otherwise occurs. Reduction in heat loss from the manifold under the hood also reduces driver discomfort in the summer when the manifold is lined in accordance with the invention. Because the insulating liner prevents rapid extraction of heat from the exhaust gases to the mufiler walls, the exhaust gases remain at much higher temperatures and can undergo secondary combustion in the system. The liner also provides an eifective surface in contact with which combustion of the gases can proceed. To aid in secondary combustion, air can be added to the exhaust gases at a point upstream of the mufller to provide additional oxygen for combustion of the remaining fuel in the exhaust gases.

It is, therefore, a principal object of the invention to provide an improved mufiling system including an interior, insulating liner. 2

Another object of the invention is to provide an exhaust system 'Where fewer deleterious substances are present in the exhausted gases.

Still another object of the invention is to provide a mufiler having a longer life than those presently known in the art.

Yet another object of the invention is to provide a mufiling system in which the exhaust gases are maintained at higher temperatures so that additional, secondary combustion can occur therein.

Other objects and advantages of the invention will be apparent from the following detailed description of a preferred embodiment thereof, reference being made to the accompanying drawings, in which:

FIG.' 1 is a somewhat schematic view, with parts broken away and parts in cross section, of an engine and a muflling system embodying the principles of the invention;

FIG. 2 is a greatly enlarged view in cross section of a muffler of the system shown in FIG. 1; E

FIG. 3 is a view in transverse cross section taken along the line 3-3 of FIG. 2;

FIG. 4 is a view in perspective of a liner segment used in the muffiing system and the mufiler of FIGS. 13;

FIG.- 5 is a view in vertical cross section of a mold for making the segment shown in FIG. 4;

FIG. 6 is a somewhat schematic view in cross section of modified apparatus for lining mufiling systems; and

FIG. 7 is a view in cross section of further modified apparatus for lining mufiling systems.

Referring to FIG. 1, an eight cylinder engine is indicated at 10, the cylinders of which are connected to a muffiing system indicated generally at 12, although the two banks of cylinders can alternately be connected to separate rnufiling systems. The system 12 includes lined manifolds 14, a lined connecting pipe 15, a lined exhaust pipe 16, a lined muffler 18, and a tailpipe 20 which can be lined or not.

The muflier 18 (FIGS. 2 and 3) includes a casing 22 comprising two half sections 24 and 26 which can be bolted together at flanges 28 and 30 (FIG. 3) extending longitudinally thereof. Suitable connecting pipes 32 and 34 (FIG. 2) are ailixed to end walls of the casing 22 for connection with the exhaust pipe 16 and the tailpipe 20,

' in a manner well known in the art. Within the casing 22 tube 36 is a cylindrical liner 40 made of a plurality of circular or ring segments 42 which are placed in coaxial, end-to-end relationship and preferably cemented together by a ceramic band. The outer diameter of the segments 42 is large enough to enable them to be held tightly within the tube 36 and the inner diameter of the segments 42 is sufiicient to form a passage for exhaust gases from the engine 10. The walls of the segments 42 are at least A" thick to provide reasonable strength and have been made in thicknesses up to approximately 1 /2" of either porous or non-porous ceramic of the type described below.

The segments 42 are integral, porous bodies containing highly refractory, titania fibers, and are self-sustaining within the tube 36, requiring no internal wall or support within the bodies. The liner 40 prevents attack of the mufiler casing by keeping any corrosive liquids in the exhaust gases out of contact therewith. The titania ceramic is also resistant to acids, to high temperature steam, and to the various corrosive contaminants within the exhaust gases. The liner 40 also acts as an extremely good insulator with the result that the temperature of the casing 22 seldom exceeds 300 F, even when the exhaust gases are at 1600 F. or higher. In addition, the exhaust gases are kept out of contact with the casing 22 to prevent an increase in the amount of olefins which might otherwise result. Finally, the exhaust gases are kept at a higher temperature within the exhaust system due to the insulating effect of the liner 40. that additional combustion of these gases can take place in order to reduce the amount of deleterious contaminants therein. For this purpose, additional air can be added to the exhaust system through an air pipe 44 (:FIG. 1), which is connected to the exhaust pipe 16. The air can be supplied by a small blower 46 or, during movement of the vehicle, by an air scoop.

,The segments 42, a single one of which is shown in perspective in FIG. 4, have been made from a mixture of 87 grams crystalline titania fibers from A" to /z" long, 20 grams of wood sawdust, 25 grams of montmorillonite and 13 grams of powdered soda-lime glass. This mixture was combined with sufiicient water to make a mortar or paste of fibrous pellets which were then pressed into a mold the size and shape of the segment 42 and fired at 2500 F. to cause the soda-lime glass and montmorillonite to form a binder for the titania fibers and to cause the sawdust to burn out and leave a porous body. The resulting body consisted essentially of 70% titania, 20% montmorillonite, and soda-lime glass. By volume, the body contained approximately 70% air, 20% titania fibers, and 10% binder (montmorillonite and sodalime glass), with an apparent density of approximately 70 pounds per cubic foot. Segments 1 thick show only slight resistance when air is blown through them.

While the segments 42 have been made in a metal mold having an annular, tapered cavity, it has been found that the material is diflicult to remove therefrom preparatory to firing. For this reason, the segments 42 are preferably made in a mold 44 shown in FIG. 5. The mold 44 includes an outer cylindrical wall 46 and anend wall 48 of paper, cardboard, or other organic material which will burn away at a temperature below the firing temperature of the segmentmaterial. A metal rod 50 which is concentric of the mold 44 extends through the end wall 48 to form an annular cavity with the end wall 48 and the cylindrical wall 46, the cavity having a shape and size similar to those of the segment 42. After the liner material is placed in the cavity and tamped therein, the metal rod 50 is removed to leave the green liner and the walls 46 and 48 which are fired as a unit, the walls 46 and 48 burning away, with only the fired, hardened segment 42 then remaining. With this arrangement, the liner material need not be removed from the mold prior to firing.

The porous liner 40 not only provides the advantages outlined above, but also constitutes an effective acoustic material to absorb sound and mufiie the noise of the exhigh temperature, had considerable tendency to warp,

haust gases and engine. The perforate tube 36 further enhances the acoustical absorption properties of the mufller 18, particularly for sound of lower'frequencyl However, the liner 4%) can be made with a larger diameter and placed immediately adjacent the casing 22, with the porous tube 36 eliminated, to provide substantially as good sound absorption. It is desirable that the muffler have a volume about ten times the volumetric displacement of the engine cylinders from an acoustical standpoint. I

In accordance with the principles of the invention, it also has been discovered that the liner material can be employed in the manifold 14 and the exhaust pipe 16 to maintain the temperature of the exhaust gases several hun dred degrees higher than otherwise and also to keep the exhaust gases separate from the steel or iron of which the manifold 14 and the exhaust pipe 16 are made to prevent reaction on the surface thereof. The manifold 14 and the exhaust pipe 16 are also maintained at cooler temperatures by being insulated from the exhaust gases, and temperatures under the hood are decreased. Because the temperatures of the lined exhaust system components are much lower than in conventional exhaust systems, the manifold 14 can be made of welded or fabricated sheet steel, the manifold 14 in this case comprising a cylin drical metal tube 52 and shorter connecting tubes 54 of welded sheet steel. Previously, it was necessary in most instances to cast the manifold 14 which, because of its making the use of fabricated steel impractical.

The manifold 14 and the exhaust pipe 16 have been lined with segments similar to the segments 42, .but of smaller diameter. However, where the manifold 14 or the exhaust pipe 16 is of relatively complicated shape, the liner can be applied to these components in the form of a thick coating on the interior walls thereof. Because sound absorption is not a consideration in the manifold 14 and the exhaust pipe 16, the liner in this case need not be porous, and the sawdust or other material forming voids in the final product need not be employed or can be employed to a lesser degree. The refractory fibers in the liner material preferably are shorter than those used in the liner 40 to enable the liner material to be more easily applied to the interior of the components. After the liner material is applied, it can be fired in the mufiling system components by passing highly heated gases therethrough to provide the proper firing temperatures therein without excessively heating the'outer walls of the components.

A thick layer of the coating material can be applied to the inner surfaces of the manifold 14 and the exhaust pipe 16 with the apparatus shown in FIG. 6. In this instance, the binder materials and the titania fibers can be supplied separately, and titania powder can be added to increase the strength of the liner. erally at 56, moves from left to right in FIG. 6 through the exhaustpipe 16, for example, which preferably is concommitantly rotated. Titania powder can first be supplied to the interior of the pipe 16 through a supply line 58 and the binder material then supplied through a second supply line 68, with the titania fibers then being supplied to the surface of the binder material through a third supply tube 62. The binder and titania also can be supplied through a single supply line as a premixed aqueous paste by means of air pressure. vThe liner material which is now deposited on the interior of the tube 16 is subsequently spread evenly by means of a spreader 64 which is in the form of a flexible cone or a plurality of flexible arms. In either case the spreader 64 is spaced from the inner surface of the pipe 16 by means of spacers 66 which determine the thickness of the liner.

A modified liner applicator 68 is shown in FIG. 7 and includes an outer passage 70 through which the binder or coating material is sprayed through an annular nozzle 72 which also can be a plurality of individual nozzles. The titania fibers are subsequently sprayed onto the wet The apparatus, indicated gencoating material by means of an inner passage 74 through which the titania fibers are blown, being deflected to the Wall of the pipe 16 by a deflector 76. Again the titania fibers and the binder material can be supplied through a single spray passage. 7

Other binders and other highly refractory fibers, such as zircon and zirconia fibers, have been found to be suitable for use in a lined muifiing system according to the invention. The fibers employed must be of a highly refractory nature, capable of withstanding temperatures of 1800 F. and preferably 2600" F. because the internal temperature of the exhaust system may be as high as 2600 F., or possibly higher, if a spark plug is inoperative and a mixture of air and raw gas is expelled into the exhaust system. However, the titania fibers, whether oxidized or oxygen deficient, have properties which render them particularly suitable for a mufiiing system, these fibers apparently having a catalytic effect-on the exhaust gases. Titania, zirconia, and zircon fibers over an inch in length and in single crystalline form have been produced in quantities according to a process set forth in a copending application of Russell, Morgan, and Schefiler filed on or about May 26, 1960.

We claim: I

1. A lined muffiing system component comprising a casing forming an elongate chamber having an inlet opening and an outlet opening, and an integral, selfisustaining liner within said chamber forming a passage for exhaust gases between said inlet opening and said outlet opening, said liner being interposed between said passage and said casing with the inne surface of said liner being substantially unobstructed for contact with exhaust gases flowing through said component, said liner comprising highly refractory, inorganic, crystalline fibers selected from the group consisting of titania, zirconia, and zircon, and an inorganic binder.

2. A lined rnufiling system component comprising a casing forming an elongate chamber having an inlet opening and an outlet opening, and an integral, self-sustaining, porous liner Within said chamber forming a passage for exhaust gases between said inlet opening and said outlet opening, said porous liner being interposed between said passage and said casing with the inner surface of said liner being substantially unobstructed for contact with exhaust gases flowing through said component, said porous liner comprising highly refractory, inorganic, titania fibers, and an inorganic binder holding said fibers together and fornnng a multiplicity of voids in said liner.

References Cited in the file of this patent UNITED STATES PATENTS 744,495 Corse Nov. 17, -3 2,041,767 Jack May 26, 1936 2,151,084 Deremer Mar. 21, 1939 2,705,541 Finch Apr. 5, 1955 2,761,525 Moss Sept. 4, 1956 2,334,425 :Rawson May 13, 1958 2,919,483 Gravley Ian. 5, 1960 2,958,388 Paulsen Nov. 1, 1960 2,974,388 Ault Mar. 14, 1961 3,009,531 Mead Nov. 21, 1961 FOREIGN PATENTS 563,110 Great Britain July 31, 1944 

1. A LINED MUFFLING SYSTEM COMPONENT COMPRISING A CASING FORMING AN ELONGATE CHAMBER HAVING AN INLET OPENING AND AN OUTLET OPENING, AND AN INTEGRAL, SELF-SUSTAINING 